Imaging element, stacked-type imaging element, imaging apparatus and electronic apparatus

ABSTRACT

There is provided an imaging device including an upper electrode; a lower electrode; a photoelectric conversion layer disposed between the upper electrode and the lower electrode; and a first organic semiconductor material including an indolocarbazole derivative and disposed between the upper electrode and the lower electrode. Further, there is provided an electronic apparatus including an imaging device that includes an upper electrode; a lower electrode; a photoelectric conversion layer disposed between the upper electrode and the lower electrode; and a first organic semiconductor material including an indolocarbazole derivative and disposed between the upper electrode and the lower electrode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/349,759 filed May 14, 2019, which is a national stage applicationunder 35 U.S.C. 371 and claims the benefit of PCT Application No.PCT/JP2017/041394 having an international filing date of 17 Nov. 2017,which designated the United States, which PCT application claimed thebenefit of Japanese Patent Application No. 2016-227291 filed 22 Nov.2016, the entire disclosures of each of which are incorporated herein byreference.

TECHNICAL FIELD

The present technology relates to an imaging element, a stacked-typeimaging element, an imaging apparatus and electronic apparatus.

BACKGROUND ART

Recently, applications of an imaging element, not only in digitalcameras and video camcorders but also in smartphone cameras,surveillance cameras, automotive back monitors, and collision preventionsensors, have widened and are receiving much attention. In order to copewith various applications, improvement of performance and functionaldiversification of imaging elements are being attempted, and advancescontinue to be made in imaging elements.

For example, a sensor including an organic photoelectric conversionelement which has an organic photoelectric conversion layer containingan organic compound refined by sublimation between a pair of electrodes,and an organic hole blocking layer disposed between one electrode andthe organic photoelectric conversion layer, and a voltage applying unitfor applying a voltage of 1.0×10⁵ V/cm to 1.0×10⁷ V/cm to the organicphotoelectric conversion layer during light irradiation, where theionization potential of the hole blocking layer is 1.3 eV or more higherthan the work function of one adjacent electrode and the electronaffinity of the hole blocking layer is equal to or higher than theelectron affinity of the adjacent organic photoelectric conversionlayer, has been proposed (see PTL 1).

Furthermore, a photoelectric conversion element including a conductivethin film, an organic photoelectric conversion film, a blocking layer,and a transparent conductive thin film, where the organic photoelectricconversion film contains a p-type organic photoelectric conversionmaterial having a glass transition point (Tg) of 100° C. or more andforming an amorphous film, and the blocking layer contains a blockingmaterial having a Tg of 140° C. or more, has been proposed (see PTL 2).

CITATION LIST Patent Literature

-   [PTL 1]-   JP 4677314B-   [PTL 2]-   JP 2014-520522A

SUMMARY Technical Problem

However, with the technologies proposed in PTLs 1 and 2, there is apossibility that further improvement of image quality and reliabilitymay not be possible.

The present technology is made in view of such a situation, and the mainpurpose of the present technology is to provide an imaging element, astacked-type imaging element, an imaging apparatus and an electronicapparatus that can further improve image quality and reliability.

Solution to Problem

Various embodiments are directed towards imaging devices that include anupper electrode; a lower electrode; a photoelectric conversion layerdisposed between the upper electrode and the lower electrode; and afirst organic semiconductor material including an indolocarbazolederivative and disposed between the upper electrode and the lowerelectrode.

Additional embodiments are directed towards an electronic apparatusincluding an imaging device that includes an upper electrode; a lowerelectrode; a photoelectric conversion layer disposed between the upperelectrode and the lower electrode; and a first organic semiconductormaterial including an indolocarbazole derivative and disposed betweenthe upper electrode and the lower electrode.

Further, the imaging devices may have the first organic semiconductormaterial disposed between the photoelectric conversion layer and thelower electrode. In various embodiments, the indolocarbazole derivativemay be selected from the group consisting of

where in the formulas (1) to (10), the Ar₁ to Ar₂₄ each independentlyrepresent an aryl group; and R₁ to R₁₀₈ each independently represent ahydrogen group, an alkyl group, an aryl group, an arylamino group, anaryl group having an arylamino group as a substituent, or a carbazolylgroup, and the formulas (1) to (10) may further be selected from thegroup consisting of

The imaging devices may have a highest occupied molecular orbital levelor work function of a p-type semiconductor contained in thephotoelectric conversion layer be from about −5.6 eV to about −5.7 eV.

The imaging devices may have a difference between a highest occupiedmolecular orbital level of the first organic semiconductor material anda highest occupied molecular orbital level or work function of a p-typesemiconductor contained in the photoelectric conversion layer be in therange of ±0.2 eV, or a difference between a highest occupied molecularorbital level of the first organic semiconductor material and thehighest occupied molecular orbital level or the work function of thep-type semiconductor be in the range of ±0.2 eV.

The imaging devices may have an indolocarbazole skeleton of theindolocarbazole derivative with intramolecular symmetry and a 5-memberedpyrrole ring; a mother skeleton of the indolocarbazole derivative havinga large size and no molecular rotation when heat, light and voltage areapplied to the mother skeleton; a mother skeleton of the indolocarbazolederivative having no molecular rotation when heat, light and voltage areapplied simultaneously to the mother skeleton; the first organicsemiconductor material being an electron blocking layer; the upperelectrode including indium-zinc oxide; and/or the lower electrodeincluding indium-tin oxide.

The imaging devices may have the photoelectric conversion layerincluding at least two materials selected from the group consisting of anaphthalene derivative, an anthracene derivative, a phenanthrenederivative, a pyrene derivative, a perylene derivative, a tetracenederivative, a pentacene derivative, a quinacridone derivative, a picenederivative, a chrysene derivative, a fluoranthene derivative, aphthalocyanine derivative, a subphthalocyanine derivative, a metalcomplex having a heterocyclic compound as a ligand, a thienoacenematerial typified by a benzothienothiophene (BTBT) derivative, adinaphthothienothiophene (DNTT) derivative, adianthracenothienothiophene (DATT) derivative, a benzobisbenzothiophene(BBBT) derivative, a thienobisbenzothiophene (TBBT) derivative, adibenzothienobisbenzothiophene (DBTBT) derivative, adithienobenzodithiophene (DTBDT) derivative, a dibenzothienodithiophene(DBTDT) derivative, a benzodithiophene (BDT) derivative, anaphthodithiophene (NDT) derivative, an anthracenodithiophene (ADT)derivative, a tetracenodithiophene (TDT) derivative, apentacenodithiophene (PDT) derivative, and a compound represented by thefollowing formula (11)

where, R₁₀₉ to R₁₁₂ each may independently represent a hydrogen group,an alkyl group, an aryl group, an arylamino group, or a carbazolylgroup, organic semiconductors having HOMO levels and LUMO levels higherthan those of p-type organic semiconductors, transparent inorganic metaloxides, a heterocyclic compound containing a nitrogen atom and an oxygenatom and a sulfur atom, organic molecules, organometallic complexes andsubphthalocyanine derivatives having pyridine, pyrazine, pyrimidine,triazine, quinoline, quinoxaline, isoquinoline, acridine, phenazine,phenanthroline, tetrazole, pyrazole, imidazole, thiazole, oxazole,benzimidazole, benzotriazole, benzoxazole, carbazole, benzofuran,dibenzofuran, fullerenes, and fullerene derivatives.

The imaging devices may further include a second organic semiconductormaterial disposed between the photoelectric conversion layer and theupper electrode, where the second organic semiconductor materialincludes at least one of pyridine, quinoline, acridine, indole,imidazole, benzimidazole, phenanthroline, and fullerenes and derivativesthereof having absorption in the visible light region from 400 nm to 700nm and typified by C60 and C70.

The imaging devices may have the indolocarbazole derivative including atleast two indole rings in one molecule.

The imaging devices may further include a second organic semiconductormaterial disposed between the photoelectric conversion layer and theupper electrode, where the upper electrode includes indium-zinc oxide,where the lower electrode includes indium-tin oxide, where thephotoelectric conversion layer includes 2 Ph-benzothienothiophene,subphthalocyanine, and C60, and where the second organic semiconductormaterial includes at least one of pyridine, quinoline, acridine, indole,imidazole, benzimidazole, phenanthroline, and fullerenes and derivativesthereof having absorption in the visible light region from 400 nm to 700nm and typified by C60 and C70.

Advantageous Effects of Invention

According to the embodiments of the present technology, image qualityand reliability can be improved. Further, the advantageous effectsdescribed above are not restrictive at all and any described in thepresent technology may be achieved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing an illustrative configuration of an imagingelement of a first embodiment to which the present technology isapplied.

FIG. 2A is a cross-sectional view showing an illustrative configurationof an imaging element of the first embodiment to which the presenttechnology is applied.

FIG. 2B is a cross-sectional view showing an illustrative configurationof an imaging element of the first embodiment to which the presenttechnology is applied.

FIG. 3 is a cross-sectional view of an illustrative portion of animaging element for evaluation used in examples.

FIG. 4 is an illustrative light absorption rate in a thickness (10 nm)of the first buffer layer formed of an indolocarbazole derivative.

FIG. 5 is an illustrative view showing usage examples of an imagingapparatus to which an embodiment of the present technology is applied.

FIG. 6 is an illustrative drawing showing the structure of C60.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments for carrying out the present technology will bedescribed. It should be noted that the embodiments described below aremerely examples of representative embodiments of the present technologyand should not be interpreted as narrowing the scope of the presenttechnology.

Further, the description will be given in the following order.

1. Overview of imaging element2. First embodiment (imaging element)3. Second embodiment (stacked-type imaging element)4. Third embodiment (imaging apparatus)5. Fourth embodiment (electronic apparatus)6. Usage examples of imaging apparatus to which present technology isapplied

1. Overview of Imaging Element

First, a summary of an imaging element according to an embodiment of thepresent technology will be described.

Photoelectric conversion by an organic semiconductor material in placeof photoelectric conversion by an inorganic semiconductor material isone example of next generation technology. Such an imaging element maybe referred to as an “organic imaging element.” Further, an imagingelement having spectral sensitivity corresponding to red, green and blueby stacking a plurality of organic semiconductor layers (referred to asa “stacked-type imaging element”) is being developed and attractingattention. Since a color separation optical system is not necessary forsuch a stacked-type imaging element and three types of electricalsignals (image signals) corresponding to red, green, and blue can beextracted from one pixel, a light utilization rate can be improved,openings expanded, and thus false signals reduced. It is said that, inthe case of the imaging element having a general color filter, about 40%of incident light is lost in the transmission absorption of the colorfilter.

Imaging elements using silicon (Si) as a photoelectric conversionmaterial have recently become mainstream. Further, there has beenminiaturization of pixels for improvement of recording density, and thepixel size has almost reached 1 The optical absorption coefficient of Siis about 10³ to 10⁴ cm⁻¹ in the visible light region, and thephotoelectric conversion layer in the imaging element is generallypositioned at a depth of 3 μm or more in the silicon semiconductorsubstrate. Here, as the pixel size is miniaturized, the aspect ratio ofthe pixel size to the depth of the photoelectric conversion layerincreases. As a result, light leakage from adjacent pixels occurs, andan incident angle of light is restricted, thereby leading to performancedegradation of the imaging element. To improve such a problem, anorganic material with a high absorption coefficient has attractedattention. In the organic imaging element or stacked-type imagingelement, the absorption coefficient of the organic material in thevisible light region can be about 10⁵ cm⁻¹ or more, the thickness of thephotoelectric conversion layer can be reduced, false color can besuppressed, sensitivity can be improved, and the number of pixels can beincreased.

While there are various problems in using organic imaging elements, atleast all of the initial characteristics of the photoelectric conversionefficiency, dark current, an SN ratio (which is the ratio of lightcurrent to dark current), afterimage characteristics, and heatresistance in the manufacturing process may be necessary to meet thestandards required for commercialization. Various efforts have been madeto solve the problems of these initial characteristics. For example,there is a technology in which dark current is not increased even if avoltage is applied from the outside to improve photoelectric conversionefficiency and responsiveness (afterimage characteristic), that is, theSN ratio (which is the ratio of light current to dark current) and theresponse characteristic can both be achieved by satisfying conditionsthat the electron affinity of the buffer layer on the anode side belower than the work function of the adjacent electrode by 1.3 eV or moreand the work function of the electron blocking layer (the first bufferlayer of an embodiment of the present technology) be equal to or lowerthan the work function of the adjacent photoelectric conversion layer.Furthermore, there is a technology that can improve resistance toheating processes (such as the process of forming the imaging element,particularly the installation of the color filter, the installation ofthe protective film, the soldering of the element, and the like), andpreservability by using an organic photoelectric conversion film whichcontains a p-type organic photoelectric conversion material having aglass transition temperature of 100° C. or more and forming an amorphousfilm, and using a material having a glass transition temperature of 140°C. or more for a buffer layer.

The above two technologies seem reasonable in consideration of thecharacteristics of organic compounds and organic semiconductor physics,but as will be shown in examples later, actual investigations have foundthat they may not be so. Further, considering use as products, it may benecessary to secure reliability against loads such as continuousapplication of voltage, heat generation in the product housing, andexternal light during photographing, among others. Organic imagingelements that satisfy both the initial characteristics and reliabilityare still under development and finding materials and new technologiesthat can achieve both characteristics has been problematic.

The inventors of the present technology have performed earnestdevelopment and found that using an indolocarbazole derivative in thefirst buffer layer of an organic imaging element leads not only toexcellent initial characteristics, such as SN ratio and afterimagecharacteristics, but is also capable of suppressing deterioration ofelectric characteristics even in a reliability test in which three loadsof light, voltage and heat are applied simultaneously and continuously.

Attempts have been made to apply an indolocarbazole derivative as a holetransport material for an organic electroluminescent device. Althoughthere is a technology relating to resistance against application of avoltage of less than 20 Vm and driving stability at 45° C. or more inthe application of six types of indolocarbazole isomers to an organicelectroluminescent device, it is not a technology for application to animaging element. Furthermore, in this technology, the number of benzenerings disposed in the central portion of the indolocarbazole skeleton isdefined as 1 to 3, and the absorption characteristics in the visiblelight region may be necessary for an organic imaging element and astacked-type imaging element (in other words, the transparency of thefirst buffer layer which absorbs light having a wavelength of 400 nm to700 nm as little as possible), is not taken into consideration. Also,spectral characteristics in the case of use as a hole transporting layerare not considered.

The present technology has been made in view of the above-mentionedsituation and enables image quality and reliability to be furtherimproved, and in particular, improves both image quality and reliabilityby using an imaging element in which at least a first electrode, a firstbuffer layer, at least a photoelectric conversion layer containing ap-type semiconductor, and a second electrode are stacked sequentially,and the first buffer layer contains an indolocarbazole derivative.

2. First Embodiment (Imaging Element)

An imaging element according to a first embodiment of the presenttechnology is an imaging element in which at least a first electrode, afirst buffer layer, at least a photoelectric conversion layer containinga p-type semiconductor, and a second electrode are stacked sequentially,and the first buffer layer contains an indolocarbazole derivative.

The imaging element according to the first embodiment of the presenttechnology, not only has excellent image characteristics (particularlyinitial characteristics of the SN ratio and the afterimagecharacteristics), but also has improved reliability that enablessuppression of the deterioration of the electric characteristics even inthe reliability test in which the three loads of “light, voltage andheat” are simultaneously and continuously applied by using anindolocarbazole derivative in the first buffer layer included in theimaging element.

FIG. 1 shows an imaging element 1-1 according to the first embodiment ofthe present technology. In the imaging element 1-1 shown in FIG. 1,light is radiated, a photoelectric conversion layer 23 is photoexcited,and carriers including holes and electrons are separated. Further, thefirst electrode from which holes are extracted is defined as an anode21, and the second electrode from which electrons are extracted isdefined as a cathode 25. The imaging element 1-1 may include a secondbuffer layer 24, and includes the first electrode (anode) 21, a firstbuffer layer 22, a photoelectric conversion layer 23 including at leasta p-type semiconductor, a second buffer layer 24 and the secondelectrode (cathode) 25 that are sequentially stacked.

FIG. 2A and FIG. 2B each show an imaging elements 1-2 and 1-3 accordingto the first embodiment of the present technology (reference number 1-2denotes an imaging element in FIG. 2A, and reference number 1-3 denotesan imaging element in FIG. 2B). In the imaging element 1-2 shown in FIG.2A, a second buffer layer 24 may be included, and a first electrode(anode) 21, a first buffer layer 22, a photoelectric conversion layer 23including at least a p-type semiconductor, a second buffer layer 24, anda second electrode (cathode) 25 are sequentially stacked on thesubstrate 20. In the imaging element 1-2, light enters from the secondelectrode (cathode) 25. In the imaging element 1-3 shown in FIG. 2B, thesecond buffer layer 24 may be included, and the second electrode(cathode) 25, the second buffer layer 24, the photoelectric conversionlayer 23 including at least a p-type semiconductor, the first bufferlayer 22, and the first electrode (anode) 21 are sequentially stacked onthe substrate 20. In the imaging element 1-3, light enters from thefirst electrode (anode) 21.

(First Buffer Layer)

The first buffer layer 22 contains an indolocarbazole derivative. Thefirst buffer layer 22 may be formed of an indolocarbazole derivative ormay be formed of an indolocarbazole derivative and at least one materialother than an indolocarbazole derivative. The film thickness of thefirst buffer layer 22 may be any thickness. In various embodiments, thefilm thickness of the first buffer layer 22 may be from about 5 nm ormore and about 50 nm or less, and it may be about 5 nm or more and about25 nm or less.

The first buffer layer 22 may have transparency, that is, it may have noabsorption in the visible light region. When the first buffer layer 22has transparency, there is an effect that the light absorption by thephotoelectric conversion layer 23 is not inhibited. Accordingly, theabsorption spectrum of the first buffer layer 22 may have an absorptionmaximum at a wavelength of 425 nm or less. In additional embodiments,the absorption spectrum of the first buffer layer 22 may have anabsorption maximum at a wavelength of 400 nm or less.

(Indolocarbazole Derivative)

The indolocarbazole derivative may contain at least two indole rings inone molecule. In various embodiments, the indolocarbazole derivative maybe a compound represented by the following general formulas (1) to (10).

When the highest occupied molecular orbital (HOMO) level of theindolocarbazole derivative is close to the HOMO level or work functionof the p-type semiconductor contained in the photoelectric conversionlayer 23, it is possible to achieve the improved image characteristicsof both the SN ratio and the afterimage characteristics. Considering theHOMO level of the indolocarbazole derivative, when the HOMO or workfunction of the p-type semiconductor contained in the photoelectricconversion layer 23 is, for example, −5.6 eV to −5.7 eV, thephotoelectric conversion rate is further improved. A compound such as aquinacridone derivative represented by the general formula (11), and athienoacene material typified by a benzothienothiophene (BTBT)derivative, a dinaphthothienothiophene (DNTT) derivative, adianthracenothienothiophene (DATT) derivative, a benzobisbenzothiophene(BBBT) derivative, a thienobisbenzothiophene (TBBT) derivative, adibenzothienobisbenzothiophene (DBTBT) derivative, adithienobenzodithiophene (DTBDT) derivative, a dibenzothienodithiophene(DBTDT) derivative, a benzodithiophene (BDT) derivative, anaphthodithiophene (NDT) derivative, an anthracenodithiophene (ADT)derivative, a tetracenodithiophene (TDT) derivative, apentacenodithiophene (PDT) derivative and the like may be used.

The difference between the HOMO level of the first buffer layercontaining the indolocarbazole derivative and the HOMO level or workfunction of the p-type semiconductor may be in the range of ±0.2 eV.According to such illustrative embodiments, the initial characteristicsof the SN ratio and the afterimage characteristics are further improved,and deterioration of electric characteristics can be further suppressedin the reliability test in which three loads of “light, voltage, heat”are continuously and simultaneously applied.

Furthermore, as a spectral characteristic, an indolocarbazole skeletonhas intramolecular symmetry, and moreover, due to inclusion of a5-membered pyrrole ring, the molecular conjugation length is suppressedwith respect to the molecular size, as compared to the condensed ring ofonly the benzene ring, and lengthening of the absorption wavelength issuppressed. Consequently, absorption in the visible region issuppressed, and light absorption by the photoelectric conversion layeris not inhibited. When an indolocarbazole derivative is used in thefirst buffer layer 22, transparency of the first buffer layer 22 can besecured.

Furthermore, the indolocarbazole derivative has a large size of themother skeleton in the whole molecule, has no molecular rotation of themother skeleton itself due to heat, light and voltage, and has no changein the molecular structure of the mother skeleton, and thus the thinfilm form of the first buffer layer can be maintained even when threeloads of heat, light and voltage are applied. Accordingly, when anindolocarbazole derivative is used in an imaging element, degradation ofan imaging element is small even if three loads of voltage, temperature,and light are simultaneously applied, and reliability can be improved.

In the above general formulas (1) to (10), Ar₁ to Ar₂₄ eachindependently represent an aryl group, and the aryl group may or may nothave a substituent. R₁ to R₁₀₈ each independently represent a hydrogengroup, an alkyl group, an aryl group, an arylamino group, an aryl grouphaving an arylamino group as a substituent, or a carbazolyl group, andthe alkyl group, the aryl group, the arylamino group, the aryl grouphaving an arylamino group as a substituent, and the carbazolyl group mayor may not have a substituent.

Each of the aryl group and the aryl group having an arylamino group as asubstituent may be a phenyl group, a biphenyl group, a naphthyl group, anaphthylphenyl group, a phenylnaphthyl group, a tolyl group, a xylylgroup, a terphenyl group, an anthracenyl group, a phenanthryl group, apyrenyl group, a tetracenyl group, a fluoranthenyl group, a pyridinylgroup, a quinolinyl group, an acridinyl group, an indole group, animidazole group, a benzimidazole group, or a thienyl group. In variousembodiments, the alkyl group may be a methyl group, an ethyl group, apropyl group, a butyl group, a pentyl group, or a hexyl group. The alkylgroup may be a linear alkyl group or a branched alkyl group.

Example compounds 100 to 150 of the compounds represented by generalformulas (1) to (10) are shown below. Further, the compounds representedby general formulas (1) to (10) are not limited to these examplecompounds.

(Imaging Element)

The imaging element 1 may be an organic imaging element having aphotoelectric conversion layer 23 which includes at least a p-typesemiconductor and is an organic photoelectric conversion layer, or maybe an inorganic imaging element in which the photoelectric conversionlayer 23 is an inorganic photoelectric conversion layer.

(Organic Imaging Element)

The organic imaging element may employ vertical spectroscopy in whichthree layers of organic photoelectric conversion elements that absorbvisible light corresponding to blue, green, and red are stackedvertically in the same pixel, or three colors of pixels may be arrangedon a plane as in a Bayer array adopted in a general imaging element.When three layers of organic photoelectric conversion elements thatabsorb visible light corresponding to blue, green, and red are stackedin the same pixel, photoelectric conversion elements that can absorblight of 425 nm to 495 nm for blue, light of 495 nm to 500 nm for green,and light of 620 nm to 750 nm for red are used. The stacking order ofthe three color photoelectric conversion elements may be in the order ofblue, green, and red in a light-incidence direction. This is becauseshorter wavelength light is more efficiently absorbed at the surface ofincidence. Red has the longest wavelength among the three colors, andthus may provide additional advantageous effects by being located at thelowermost layer as viewed from a light-incidence surface. Green may belocated at the middle among the two colors, but may be located at theuppermost layer with respect to the light-incidence surface. Thecharacteristics of the present vertical spectroscopy include that,unlike Bayer array elements, spectroscopy for blue, green, and red isnot performed using a color filter, and blue, green, and red pixels arenot arranged on a plane, but photoelectric conversion elements of thethree colors are stacked in parallel with the light-incidence directionin the same pixel, and thus sensitivity and recording density per unitvolume can be improved. Furthermore, since an organic material has ahigh absorption coefficient, a film thickness of a photoelectricconversion layer of each color can be thinner than in a conventionalSi-based photoelectric conversion layer, and light leakage from adjacentpixels and restriction on the light-incidence angle can be alleviated.Moreover, since the conventional Si-based imaging element produces colorsignals by performing interpolation processing among three-color pixels,false color is generated, but a stacked-type imaging element has anadvantage in that false color can be suppressed. On the other hand, acolor filter is generally used when three-color pixels are arranged on aplane as in a Bayer array, and thus it is considered that thespecification of spectral characteristics of blue, green and red can bealleviated as compared to a photoelectric conversion layer usingvertical spectroscopy, and mass productivity is also improved ascompared to vertical spectroscopy.

(Inorganic Imaging Element)

The inorganic imaging element may include a Si-based photoelectricconversion layer, and for example, a backside illumination type imagingelement as described in JP 2014-127545A may be used.

(Photoelectric Conversion Layer)

Hereinafter, the photoelectric conversion layer 23 will be describedseparately with respect to an organic photoelectric conversion layer andinorganic photoelectric conversion layer.

(Organic Photoelectric Conversion Layer)

The organic photoelectric conversion layer is formed of (1) a p-typeorganic semiconductor. The organic photoelectric conversion layer isformed of (2) a stacked structure of a p-type organic semiconductorlayer/an n-type organic semiconductor layer. The organic photoelectricconversion layer is formed of a stacked structure of a p-type organicsemiconductor layer/a mixed layer (bulk hetero structure) of a p-typeorganic semiconductor and an n-type organic semiconductor/an n-typeorganic semiconductor layer. The organic photoelectric conversion layeris formed of a stacked structure of p-type organic semiconductor layer/amixed layer (bulk hetero structure) of a p-type organic semiconductorand an n-type organic semiconductor. The organic photoelectricconversion layer is formed of a stacked structure of an n-type organicsemiconductor layer/a mixed layer (bulk hetero structure) of a p-typeorganic semiconductor and an n-type organic semiconductor. The organicphotoelectric conversion layer is formed of (3) a mixture (bulk heterostructure) of a p-type organic semiconductor and an n-type organicsemiconductor.

The organic photoelectric conversion layer may be formed by any one ormore of the above three embodiments (1) to (3).

Further, one type of the p-type semiconductor and n-type semiconductormay be contained in the same layer, and two or more types thereof may becontained in the same layer. For example, the material forming the bulkhetero layer includes not only two types but also three or more types.

Examples of the p-type organic semiconductor include a naphthalenederivative, an anthracene derivative, a phenanthrene derivative, apyrene derivative, a perylene derivative, a tetracene derivative, apentacene derivative, a quinacridone derivative, a picene derivative, achrysene derivative, a fluoranthene derivative, a phthalocyaninederivative, a subphthalocyanine derivative, a metal complex having aheterocyclic compound as a ligand, a thienoacene material typified by abenzothienothiophene (BTBT) derivative, a dinaphthothienothiophene(DNTT) derivative, a dianthracenothienothiophene (DATT) derivative, abenzobisbenzothiophene (BBBT) derivative, a thienobisbenzothiophene(TBBT) derivative, a dibenzothienobisbenzothiophene (DBTBT) derivative,a dithienobenzodithiophene (DTBDT) derivative, adibenzothienodithiophene (DBTDT) derivative, a benzodithiophene (BDT)derivative, a naphthodithiophene (NDT) derivative, ananthracenodithiophene (ADT) derivative, a tetracenodithiophene (TDT)derivative, a pentacenodithiophene (PDT) derivative, etc.

A p-type organic semiconductor which is one type of p-type semiconductormay be a compound represented by the following general formula (11).

In the general formula (11), R₁₀₉ to R₁₁₂ each independently represent ahydrogen group, an alkyl group, an aryl group, an arylamino group, or acarbazolyl group, and the alkyl group, the aryl group, the arylaminogroup, and the carbazolyl group may or may not have a substituent.

Each of the aryl group and the aryl group having an arylamino group as asubstituent may be a phenyl group, a biphenyl group, a naphthyl group, anaphthylphenyl group, a phenylnaphthyl group, a tolyl group, a xylylgroup, a terphenyl group, an anthracenyl group, a phenanthryl group, apyrenyl group, a tetracenyl group, a fluoranthenyl group, a pyridinylgroup, a quinolinyl group, an acridinyl group, an indole group, animidazole group, a benzimidazole group, or a thienyl group. The alkylgroup may be a methyl group, an ethyl group, a propyl group, a butylgroup, a pentyl group, or a hexyl group. The alkyl group may be a linearalkyl group or a branched alkyl group.

Examples of the n-type organic semiconductor include fullerenes andfullerene derivatives, organic semiconductors having HOMO levels andlowest unoccupied molecular orbital (LUMO) levels higher (deeper) thanthose of p-type organic semiconductors, transparent inorganic metaloxides, etc. Specific examples of the n-type organic semiconductorinclude a heterocyclic compound containing a nitrogen atom, an oxygenatom and a sulfur atom, for example, organic molecules, organometalliccomplexes and subphthalocyanine derivatives having pyridine, pyrazine,pyrimidine, triazine, quinoline, quinoxaline, isoquinoline, acridine,phenazine, phenanthroline, tetrazole, pyrazole, imidazole, thiazole,oxazole, benzimidazole, benzotriazole, benzoxazole, carbazole,benzofuran, dibenzofuran and the like as a part of the molecularskeleton, fullerenes and fullerene derivatives, etc.

The thickness of the organic photoelectric conversion layer is notlimited, but may be, for example, 10 nm to 500 nm, or 25 nm to 300 nm,or 25 nm to 250 nm, or 100 nm to 180 nm. Moreover, an organicsemiconductor is often classified as p-type or n-type, but p-type meansthat holes can be easily transported, and n-type means that electronscan be easily transported, and an organic semiconductor is not limitedto the interpretation that it has holes or electrons as majoritycarriers of thermal excitation like inorganic semiconductors.

(Inorganic Photoelectric Conversion Layer)

In addition to crystalline silicon, examples of inorganic materialsforming the photoelectric conversion layer 23 include amorphous silicon,microcrystalline silicon, crystalline selenium, amorphous selenium, andcompound semiconductors such as chalcopyrite compounds such as CIGS(CuInGaSe), CIS (CuInSe₂), CuInS₂, CuAlS₂, CuAlSe₂, CuGaS₂, CuGaSe₂,AgAlS₂, AgAlSe₂, AgInS₂ and AgInSe₂, or group III-V compounds such asGaAs, InP, AlGaAs, InGaP, AlGaInP and InGaAsP, and CdSe, CdS, In₂Se₃,In₂S₃, Bi₂Se₃, Bi₂S₃, ZnSe, ZnS, PbSe, PbS, etc. In addition, it is alsopossible to use quantum dots formed of these materials for the inorganicphotoelectric conversion layer.

(Second Buffer Layer)

The second buffer layer 24 may be inserted between the second electrode(cathode) 25 and the photoelectric conversion layer 23. As a materialused in the second buffer layer 24, a material having a work functionhigher (deeper) than that of the material used in the first buffer layer22 may be used. For example, materials which are organic molecules andorganometallic complexes having a heterocycle containing N such aspyridine, quinoline, acridine, indole, imidazole, benzimidazole, orphenanthroline as a part of the molecular skeleton, and have lowabsorption in the visible light region, may be used. Furthermore, in thecase of forming a cathode side organic carrier blocking layer using athin film of about 5 nm to 20 nm, fullerenes and derivatives thereofhaving absorption in the visible light region from 400 nm to 700 nm andtypified by C60 and C70 may be used. However, the second buffer layer 24used in the imaging element 1 according to the first embodiment of thepresent technology is not limited thereto.

(First Semiconductor Layer)

In order to improve the electrical bondability between the first bufferlayer 22 and the first electrode (anode) 21 or the photoelectricconversion layer 23, or to adjust the electric capacity of thephotoelectric conversion element, the first buffer layer may include afirst semiconductor layer (not shown) adjacent to the first buffer layer22. Examples of materials of the first semiconductor layer includecompounds such as aromatic amine-based materials typified bytriarylamine compounds, benzidine compounds, styrylamine compounds,carbazole derivatives, naphthalene derivatives, anthracene derivatives,phenanthrene derivatives, pyrene derivatives, perylene derivatives,tetracene derivatives, pentacene derivatives, picene derivatives,chrysene derivatives, fluoranthene derivatives, phthalocyaninederivatives, subphthalocyanine derivatives, hexaazatriphenylenederivatives, metal complexes having a heterocyclic compound as a ligand,thienoacene materials typified by benzothienothiophene (BTBT)derivatives, dinaphthothienothiophene (DNTT) derivatives,dianthracenothienothiophene (DATT) derivatives, benzobisbenzothiophene(BBBT) derivatives, thienobisbenzothiophene (TBBT) derivatives,dibenzothienobisbenzothiophene (DBTBT) derivatives,dithienobenzodithiophene (DTBDT) derivatives, dibenzothienodithiophene(DBTDT) derivatives, benzodithiophene (BDT) derivatives,naphthodithiophene (NDT) derivatives, anthracenodithiophene (ADT)derivatives, tetracenodithiophene (TDT) derivatives andpentacenodithiophene (PDT) derivatives,poly(3,4-ethylenedioxythiophene)/polystyrenesulfonic acid (PEDOT/PSS),polyaniline, molybdenum oxide (MoOx), ruthenium oxide (RuOx), vanadiumoxide (VOx), tungsten oxide (WOx), etc. Particularly, in the case ofincreasing the film thickness of the semiconductor layer for the purposeof greatly reducing the electric capacity, thienoacene derivatives(material) typified by benzothienothiophene (BTBT) derivatives may beused.

(Film-Forming Method of First Buffer Layer, Photoelectric ConversionLayer, Second Buffer Layer and First Semiconductor Layer)

A dry film formation method and a wet film formation method are examplesof a film-forming method for the first buffer layer 22, thephotoelectric conversion layer 23, the second buffer layer 24 and thefirst semiconductor layer. Examples of the dry film formation methodinclude a vacuum deposition method using resistance heating or highfrequency heating, an EB vapor deposition method, various sputteringmethods (a magnetron sputtering method, an RF-DC coupled bias sputteringmethod, an ECR sputtering method, a facing-target sputtering method anda high frequency sputtering method), an ion plating method, a laserablation method, a molecular beam epitaxy method, and a laser transfermethod. Furthermore, examples of a chemical vapor deposition (CVD)method include a plasma CVD method, a thermal CVD method, an MOCVDmethod, and a photo CVD method. On the other hand, as a wet method,methods such as a spin coating method, an inkjet method, a spray coatingmethod, a stamp method, a microcontact printing method, a flexographicprinting method, an offset printing method, a gravure printing method, adipping method and the like may be used. For patterning, chemicaletching such as shadow mask, laser transfer, photolithography and thelike, and physical etching by ultraviolet light, laser and the like maybe used. Examples of a planarization technology include a laserplanarization method, a reflow method, etc.

(First Electrode and Second Electrode)

The first electrode (anode) 21 and the second electrode (cathode) 25 maybe formed of a transparent conductive material. In the case of forming astacked-type imaging element according to a second embodiment of thepresent technology which will be described later, the first electrode(anode) 21 and the second electrode (cathode) 25 may be formed of atransparent conductive material. When the imaging element or the likeaccording to the first embodiment of the present technology is arrangedon a plane as in a Bayer array, for example, one of the first electrode(anode) 21 and the second electrode (cathode) 25 may be formed of atransparent conductive material, and the other may be formed of a metalmaterial. In this case, as shown in FIG. 2B, the first electrode 21located on the light incident side may be formed of a transparentconductive material, and the second electrode 25 may be formed ofaluminum (Al), an alloy of aluminum, silicon and copper (Al—Si—Cu) or analloy of magnesium and silver (Mg—Ag). Alternatively, as shown in FIG.2A, the second electrode 25 located on the light incident side may beformed of a transparent conductive material, and the first electrode 21may be formed of an alloy of aluminum and neodymium (Al—Nd) or an alloyof aluminum, samarium and copper (ASC). Further, an electrode formed ofa transparent conductive material may be referred to as a “transparentelectrode.” Here, examples of the transparent conductive materialforming the transparent electrode include conductive metal oxides, andspecific examples thereof include indium oxide, indium-tin oxide (ITOincluding Sn-doped In₂O₃, crystalline ITO and amorphous ITO),indium-zinc oxide (IZO) in which indium is added to zinc oxide as adopant, indium-gallium oxide (IGO) in which indium is added to galliumoxide as a dopant, indium-gallium-zinc oxide (IGZO, In—GaZnO₄) in whichindium and gallium are added to zinc oxide as a dopant, IFO (F-dopedIn₂O₃), tin oxide (SnO₂), ATO (Sb-doped SnO₂), FTO (F-doped SnO₂), zincoxide (including ZnO doped with other elements), aluminum-zinc oxide(AZO) in which aluminum is added to zinc oxide as a dopant, gallium-zincoxide (GZO) in which gallium is added to zinc oxide as a dopant,titanium oxide (TiO₂), antimony oxide, a spinel type oxide, and an oxidehaving an YbFe₂O₄ structure. Alternatively, a transparent electrodehaving a mother layer of gallium oxide, titanium oxide, niobium oxide,nickel oxide or the like may be given as an example. The thickness ofthe transparent electrode may be 2×10⁻⁸ m to 2×10⁻⁷ m, or 3×10⁻⁸ m to1×10⁻⁷ m.

Furthermore, when transparency is unnecessary, a conductive materialforming an anode having a function as an electrode for extracting holesmay be a conductive material having a high work function (e.g., ϕ=4.5 eVto 5.5 eV), and specific examples thereof include gold (Au), silver(Ag), chromium (Cr), nickel (Ni), palladium (Pd), platinum (Pt), iron(Fe), iridium (Ir), germanium (Ge), osmium (Os), rhenium (Re), andtellurium (Te). On the other hand, a conductive material forming acathode having a function as an electrode for extracting electrons maybe a conductive material having a low work function (e.g., ϕ=3.5 eV to4.5 eV), and specific examples thereof include alkali metals (e.g., Li,Na, K, etc.) and fluorides or oxides thereof, alkaline earth metals(e.g., Mg, Ca, etc.) and fluorides or oxides thereof, aluminum (Al),zinc (Zn), tin (Sn), thallium (Tl), a sodium-potassium alloy, analuminum-lithium alloy, a magnesium-silver alloy, indium and rare earthmetals such as ytterbium, or alloys thereof. Alternatively, examples ofthe material forming an anode or cathode include metals such as platinum(Pt), gold (Au), palladium (Pd), chromium (Cr), nickel (Ni), aluminum(Al), silver (Ag), tantalum (Ta), tungsten (W), copper (Cu), titanium(Ti), indium (In), tin (Sn), iron (Fe), cobalt (Co), molybdenum (Mo) orthe like, or alloys including these metal elements, conductive particlesformed of these metals, conductive particles of alloys including thesemetals, polysilicon containing impurities, carbon-based materials, oxidesemiconductors, conductive materials such as carbon nanotubes, grapheneand the like, and a stacked structure of layers containing theseelements. Furthermore, examples of a material forming an anode orcathode include organic materials (conductive polymers) such aspoly(3,4-ethylenedioxythiophene)/polystyrenesulfonic acid (PEDOT/PSS).Further, a paste or ink prepared by mixing these conductive materialsinto a binder (polymer) may be cured to be used as an electrode.

The first electrode (anode) 21 and second electrode (cathode) 25 may becoated with a coating layer. Examples of materials forming the coatinglayer include inorganic insulating materials exemplified by a metaloxide high-dielectric constant insulating film such as siliconoxide-based materials, silicon nitride (SiNY), aluminum oxide (Al₂O₃) orthe like as well as organic insulating materials (organic polymers)exemplified by polymethyl methacrylate (PMMA), polyvinyl phenol (PVP),polyvinyl alcohol (PVA), polyimide, polycarbonate (PC), polyethyleneterephthalate (PET), polystyrene, silanol derivatives (silane couplingagents) such as N-2(aminoethyl)3-aminopropyltrimethoxysilane (AEAPTMS),3-mercaptopropyltrimethoxysilane (MPTMS), octadecyltrichlorosilane (OTS)or the like, straight-chain hydrocarbons having a functional groupcapable of bonding to the electrode at one end such as octadecanethiol,dodecyl isocyanate and the like, and combinations thereof. In addition,examples of the silicon oxide-based materials include silicon oxide(SiOx), BPSG, PSG, BSG, AsSG, PbSG, silicon oxynitride (SiON),spin-on-glass (SOG), and low dielectric constant materials (e.g.,polyaryl ether, cycloperfluorocarbon polymers, benzocyclobutene, cyclicfluoro resins, polytetrafluoroethylene, fluoroaryl ether, fluorinatedpolyimide, amorphous carbon and organic SOG). As a method for formingthe insulating layer, for example, the dry film formation methods andthe wet film formation methods described above may be used.

(Film-Forming Method of First Electrode and Second Electrode)

A dry method or wet method may be used as a film-forming method of thefirst electrode (anode) 21 and the second electrode (cathode) 25.Examples of the dry method include a physical vapor deposition method(PVD method) and a chemical vapor deposition method (CVD method).Examples of the film-forming method using the principle of a PVD methodinclude a vacuum deposition method using resistance heating or highfrequency heating, an electron beam (EB) deposition method, varioussputtering methods (a magnetron sputtering method, an RF-DC coupled biassputtering method, an ECR sputtering method, a facing-target sputteringmethod and a high-frequency sputtering method), an ion plating method, alaser ablation method, a molecular beam epitaxy method, and a lasertransfer method. Furthermore, examples of the CVD method include aplasma CVD method, a thermal CVD method, an organic metal (MO) CVDmethod, and a photo CVD method. On the other hand, examples of the wetmethod include an electrolytic plating method and an electroless platingmethod, a spin coating method, an ink jet method, a spray coatingmethod, a stamping method, a micro contact printing method, aflexographic printing method, an offset printing method, a gravureprinting method, a dipping method, etc. For patterning, chemical etchingsuch as shadow mask, laser transfer, photolithography and the like,physical etching by ultraviolet light, laser and the like may be used.Examples of a planarization technology include a laser planarizationmethod, a reflow method, a chemical mechanical polishing (CMP) method,etc.

(Substrate)

The imaging element 1 may be formed on a substrate 20. Here, examples ofthe substrate 20 include organic polymers (having a form of a polymericmaterial such as a plastic film, a plastic sheet or a plastic substrateformed of polymeric materials and having flexibility) exemplified bypolymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polyvinylphenol(PVP), polyethersulfone (PES), polyimide, polycarbonate (PC),polyethylene terephthalate (PET), and polyethylene naphthalate (PEN).When such a substrate formed of the polymeric material havingflexibility is used, for example, it is possible to incorporate orintegrate an imaging element in electronics having a curved surfaceshape. Alternatively, examples of the substrate 20 include various glasssubstrates, various types of glass substrates having an insulating filmformed on surfaces thereof, quartz substrates, quartz substrates havingan insulating film formed on surfaces thereof, silicon semiconductorsubstrates, metal substrates formed of various alloys and metals such asstainless steel and having an insulating film formed on surfacesthereof. Further, examples of the insulating film include siliconoxide-based material (e.g., SiOx or spin-on-glass (SOG)), siliconnitride (SiN_(Y)), silicon oxynitride (SiON), aluminum oxide (Al₂O₃),metal oxides and metal salts. Furthermore, it is also possible to forman insulating film formed of an organic material. Examples thereofinclude lithographically processable polyphenol-based materials,polyvinyl phenol-based materials, polyimide-based materials,polyamide-based materials, polyamideimide-based materials,fluorine-based polymeric materials, borazine-silicon polymericmaterials, torquecene-based materials, etc. Further, a conductivesubstrate (a substrate formed of a metal such as gold or aluminum, asubstrate formed of highly oriented graphite) having these insulatingfilms formed on a surface thereof may also be used. The surface of thesubstrate 20 may be smooth, but may have roughness to an extent thatdoes not adversely affect the characteristics of the organicphotoelectric conversion layer. The adhesion between the first electrode(anode) 21 and the substrate 20 or the adhesion between the secondelectrode (cathode) 25 and the substrate 20 may be improved by forming asilanol derivative on the surface of the substrate by a silane couplingmethod, or forming a thin film formed of a thiol derivative, acarboxylic acid derivative, a phosphoric acid derivative or the like bythe SAM method or the like, or forming a thin film formed of aninsulating metal salt or metal complex by a CVD method or the like.

In the imaging element according to the first embodiment of the presenttechnology, an on-chip microlens or a light-shielding layer may befurther provided, or a driving circuit or a wiring for driving theimaging element according to the first embodiment of the presenttechnology may be provided. As necessary, a shutter for controllingincidence of light on the imaging element according to the firstembodiment may be provided.

3. Second Embodiment (Stacked-Type Imaging Element)

The stacked-type imaging element according to the second embodiment ofthe present technology is an imaging element in which at least two ofthe imaging elements according to the first embodiment of the presenttechnology are stacked. The imaging elements to be stacked may be acombination of an organic imaging element and inorganic imaging element,or only organic imaging elements, or only inorganic imaging elements.

(Regarding Imaging Element in which Organic Imaging Element andInorganic Imaging Element are Stacked)

As described above, the stacked-type imaging element according to thesecond embodiment of the present technology may be an element in whichone or two layers of organic photoelectric conversion elements andinorganic photoelectric conversion elements are combined. In the case ofusing vertical spectroscopy, as for the stacking order of thephotoelectric conversion element, an inorganic photoelectric conversionelement may be located at the lowermost layer as viewed from thelight-incident direction. Since it may be ideal to locate an organicphotoelectric conversion element at the upper layer with respect to thelight-incident direction, in the case of one layer (single layerelement), a blue or green photoelectric conversion element may be used,and in the case of two layers (stack of two color elements), a bluecolor may be the first layer and a green color may be the second layer,and vice versa. Regarding the visible light absorption wavelength ofeach color, it is the same as the wavelength range described in theorganic imaging element, and the stacked-type imaging element can absorblight of 425 nm to 495 nm for blue, light of 495 nm to 500 nm for green,and light of 620 nm to 750 nm for red.

JP 2014-127545A provides an example of an imaging element in which anorganic imaging element and an inorganic imaging element are stacked.However, although an organic photoelectric conversion element isdescribed as being capable of obtaining a green color signal in thispatent, the stacked-type imaging element of the present patent is notlimited thereto. The present stacked-type imaging element has advantagesof sensitivity, recording density, light leakage, restriction onlight-incident angle, and reduction of false color described in thesection of the organic imaging element. Furthermore, the organicphotoelectric conversion layer and inorganic photoelectric conversionlayer may be arrayed on a plane as in a Bayer array. In this case, it isconsidered that the specification of spectral characteristics of blue,green and red can be alleviated as compared to a photoelectricconversion layer using vertical spectroscopy, and mass productivity isalso improved as compared to vertical spectroscopy.

In the stacked-type imaging element according to the second embodimentof the present technology, an on-chip microlens or a light-shieldinglayer may be further provided as necessary, or a driving circuit or awiring for driving the stacked-type imaging element according to thesecond embodiment of the present technology may be provided. Asnecessary, a shutter for controlling incidence of light into thestacked-type imaging element according to the second embodiment may beprovided.

4. Third Embodiment (Imaging Apparatus)

The imaging apparatus according to a third embodiment of the presenttechnology is an apparatus including a plurality of the imaging elementsaccording to the first embodiment of the present technology, or anapparatus including a plurality of the stacked-type imaging elementaccording to the second embodiment of the present technology.

In the imaging apparatus according to the third embodiment of thepresent technology, an on-chip microlens or a light-shielding layer maybe further provided as necessary. An optical cut filter may be providedin accordance with the purpose of the imaging apparatus according to thethird embodiment of the present technology. Furthermore, examples of thearrangement of the imaging element according to the first embodiment ofthe present technology or the stacked-type imaging element according tothe second embodiment of the present technology in the imaging apparatusaccording to the third embodiment of the present technology include aninterline arrangement, a G stripe-RB checkered array, a G stripe-RBfull-checkered array, a checkered complementary color array, a stripearray, a diagonal stripe array, a primary color difference array, afield color difference sequential array, a flame color differencesequential array, an MOS-type array, a modified MOS-type array, a flameinterleave array and a field interleave array in addition to a Bayerarray.

5. Fourth Embodiment (Electronic Apparatus)

The electronic apparatus according to a fourth embodiment of the presenttechnology is an apparatus including the imaging apparatus according tothe third embodiment of the present technology.

6. Usage Examples of Imaging Apparatus to which Present Technology isApplied

FIG. 5 is a diagram illustrating usage examples in which theabove-described imaging apparatus is used. For example, theabove-described imaging apparatus can be used for various cases in whichlight such as visible light, infrared light, ultraviolet light, orX-rays is detected as follows.

-   -   Devices that take images used for viewing, such as a digital        camera and a portable appliance with a camera function.    -   Devices used for traffic, such as an in-vehicle sensor that        takes images of the front and the back of a car, surroundings,        the inside of the car, and the like, a monitoring camera that        monitors travelling vehicles and roads, and a distance sensor        that measures distances between vehicles and the like, which are        used for safe driving (e.g., automatic stop), recognition of the        condition of a driver, and the like.    -   Devices used for home electrical appliances, such as a TV, a        refrigerator, and an air conditioner, to take images of a        gesture of a user and perform appliance operation in accordance        with the gesture.    -   Devices used for medical care and health care, such as an        endoscope and a device that performs angiography by reception of        infrared light.    -   Devices used for security, such as a monitoring camera for crime        prevention and a camera for personal authentication.    -   Devices used for beauty care, such as skin measurement equipment        that takes images of the skin and a microscope that takes images        of the scalp.    -   Devices used for sports, such as an action camera and a wearable        camera for sports and the like.    -   Devices used for agriculture, such as a camera for monitoring        the condition of fields and crops.

In addition, embodiments of the present technology are not limited tothe above-described embodiments, and various alterations may occurinsofar as they are within the scope of the present technology.

Note that the effects described in the present specification are merelyillustrative examples and not limitative; other effects may beexhibited.

Additionally, the present technology may also be configured as describedbelow.

EXAMPLES

Hereinafter, effects of the present technology will be described indetail with reference to examples. Further, the scope of the presenttechnology is not limited to the examples.

Example 1

An imaging element for evaluation represented by a schematic partialcross-sectional view shown in FIG. 3 was prepared by the followingmethod. Further, an imaging element for green was used as the imagingelement for evaluation.

(Preparation of Organic Imaging Element)

An ITO film was formed to a thickness of 120 nm on a quartz substrate bya sputtering apparatus and a first electrode formed of ITO was formed onthe basis of a lithography technology using a photomask. Subsequently,an insulating layer was formed on the quartz substrate and the firstelectrode, pixels were formed so as to expose an ITO first electrode of1 mm square is exposed by a lithography technology, followed byultrasonic cleaning sequentially with a neutral detergent, acetone andethanol. After drying this ITO substrate, an UV/ozone treatment wasfurther carried out for 10 minutes. Thereafter, after the ITO substratewas fixed to a substrate holder of a vapor deposition apparatus, a vapordeposition tank was depressurized to 5.5×10⁻⁵ Pa.

Thereafter, a first buffer layer with a thickness of 5 nm was formed byvacuum deposition film formation using a shadow mask using materials ofCompounds A to F having the physical property values shown in Table 1and having the molecular structure shown below. Subsequently, a p-typeorganic semiconductor layer having a thickness of 5 nm in aphotoelectric conversion layer was formed using a quinacridonederivative (BQD) substituted with a t-butyl group in the sameevaporator. Further, BQD and fluorinated subphthalocyanine chloride(F6-SubPc-C1) were co-deposited to a thickness of 150 nm at a depositionspeed ratio of 1:1 to form a photoelectric conversion layer by a mixedlayer (bulk hetero structure) of a p-type organic semiconductor and ann-type organic semiconductor. Subsequently, B4PyMPM was deposited to athickness of 5 nm to form a second buffer layer. Then, the second bufferlayer was placed in a container that can be transported in an inertatmosphere, transported to a sputtering apparatus, and ITO was depositedto a thickness of 50 nm on the upper layer of B4PyMPM to form a secondelectrode. Thereafter, in a nitrogen atmosphere, annealing whichsimulates a process for forming the actual imaging element,particularly, a heating process such as installation of a color filter,installation of a protective film, soldering of an element and the likewas performed at 150° C. for 2.5 hours to prepare an organic imagingelement.

Furthermore, the physical property values shown in the following Table 1were evaluated by the following method. HOMO (ionization potential) wasobtained by forming each of Compounds A to F to a thickness of 20 nm ona Si substrate and measuring thin film surface thereof by ultravioletphotoelectron spectroscopy (UPS). Further, an optical energy gap wascalculated from the absorption end of the absorption spectrum of thethin film of each material and LUMO was calculated from the differencebetween HOMO and the energy gap (LUMO=−1*|HOMO-energy gap|). Formobility, an element for measuring mobility was prepared and evaluatedby the following method. First, a thin film of Pt was formed at athickness of 100 nm by an EB vapor deposition method and a firstelectrode of Pt was formed on the basis of a lithography technologyusing a photomask. Next, an insulating layer was formed on the substrateand the Pt first electrode, pixels were formed so that the Pt firstelectrode of 0.25 mm square was exposed by a lithography technology, anda molybdenum oxide (MoO₃) film with a thickness of 1 nm, films ofCompounds A to F of which the mobility is to be measured with athickness of 200 nm, a molybdenum oxide (MoO₃) film with a thickness of3 nm, and an Au second electrode with a thickness of 100 nm each werestacked and formed thereon. A voltage of −1 V to −20 V or a voltage of+1 V to +20 V was applied to the element for mobility film formationobtained by the above-described method, the formula of space chargelimited current (SCLC) was fitted to a current-voltage curve where morecurrent was flowed by a negative bias or a positive bias, and themobility at −1 V or +1 V was measured.

The glass transition temperatures of Compounds A to F were measuredusing a device manufactured by Seiko Instruments Inc. (model name: DSC6200). Each sample of Compounds A to F was weighed by 5 to 10 mg andplaced in a sample pan and heated to a melting temperature at a heatingrate of 20° C./min under N2 atmosphere to perform a first measurement.Thereafter, the sample pan was taken out of the apparatus, placed on anAl block and quenched. Subsequently, in a second measurement, heatingwas performed from 30° C. to a melting point at a heating rate of 20°C./min, and the temperature at which the second phase transitionappeared was measured as the glass transition temperature.

(Evaluation of Organic Imaging Element)

The organic imaging element thus obtained was placed on a prober stageof which the temperature was controlled to 60° C. and a voltage of −1 Vwas applied between the second electrode and first electrode whileperforming light irradiation under the conditions of a wavelength of 560nm and 2 μW/cm² to measure bright current. Thereafter, light irradiationwas stopped and dark current was measured. The results of calculating anexternal quantum efficiency (EQE=|((light current-darkcurrent)×100/(2×10{circumflex over ( )}−6))×(1240/560)×100|) and an SNratio (SN ratio=Log(light current-dark current)/dark current)) from thebright current and dark current are shown in Table 1. Furthermore, asfor the afterimage evaluation, light having a wavelength of 560 nm andan intensity of 2 μW/cm² was irradiated while applying −1 volt(so-called reverse bias voltage of 1 volt) between the second electrodeand the first electrode, and subsequently, when light irradiation wasstopped, the amount of current flowing between the second electrode andthe first electrode immediately before the light irradiation was stoppedwas defined as I₀ and the time from the stop of light irradiation untilthe current amount reaches (0.03×I₀) was defined as T₀, and T₀ wasdefined as the afterimage time, and are shown in Table 1. However, thedark current, the external quantum efficiency, and the afterimage T₀ arerepresented by relative values when the value of Compound A is 1.

Referring to Table 1, the SN ratio of the four materials of Compounds Cto F was close to 4 and excellent imaging characteristics were obtained.This is because the deeper the HOMO level, the more dark current issuppressed in consideration of the SN ratio formula. In any one of thefirst buffer layer materials (compounds A to F) used in the presentstudy, the LUMO level was shallower than −3 eV, and there is an energybarrier because the work function (−4.8 eV) of the first electrode andthe LUMO level of the first buffer layer were separated by about 1.8 eV.As a result, it is considered that electron injection from the firstelectrode (ITO) into the organic photoelectric conversion layer via theLUMO level of the first buffer layer is suppressed in the dark. However,dark current source may be caused not only by electron injection fromthe first electrode via the first buffer layer, but also by carriersgenerated in the photoelectric conversion layer or in the interfacebetween the first buffer layer and the photoelectric conversion layer(grain of p-type organic semiconductor) (internal generation of darkcurrent). Particularly, although the cause of the internal occurrence ofthe dark current has not been investigated in the conventionaltechnology, it is considered that, from the study result of examples 1,deepening of the HOMO level of the first buffer layer is effective as acountermeasure against the internal generation of the dark current. Inother words, it may be necessary not only to obtain excellent lightcurrent but also to suppress dark current in order to improve the SNratio, and also, it may be important to lower the HOMO level and preventinternally generated carriers from leakage in addition to preventingcarrier injection from the first electrode by increasing the LUMO levelof the first buffer layer.

On the other hand, the afterimage characteristics of Compounds A to Eare excellent, but Compound F has about 2 times afterimage value. It canbe considered that “the bonding state between the HOMO level of thefirst buffer material and the HOMO level of a p material in thephotoelectric conversion layer” and “the hole mobility of the firstbuffer material” are involved in the afterimage characteristics. Thehole mobility of the first buffer material group used in Example 1 has adifference of about one digit, and it turns out that there is nocorrelation between the mobility and the afterimage value when thecorrelation between the mobility and the afterimage value is actuallyexamined. On the other hand, it turns out that, as shown in Table 1, thematerial having a high HOMO level has an excellent afterimage value,when noting “the bonding state between the HOMO level of the firstbuffer material and the HOMO level of a p material in the photoelectricconversion layer” and investigating a correlation of the HOMO level withrespect to the afterimage value. Regarding this mechanism, it isconsidered because a barrier is formed between the grain of the p-typeorganic semiconductor and the first buffer layer, and thereby theafterimage characteristics are deteriorated in the case where the HOMOof the first buffer layer is too deep when the carriers in theafterimage evaluation under reverse bias of −1 V in the afterimageevaluation. When it is taken into consideration together with theresults of the SN ratio, in the case where the HOMO level of the firstbuffer layer is higher as compared to the HOMO level of the grain of thep-type organic semiconductor, the dark current characteristics are notgood while the afterimage characteristics are excellent. Furthermore, inthe case of the reversed energy level relation, whether the afterimagecharacteristics and the dark current are excellent or not is alsoreversed. That is, it may be that the energy level of the first bufferlayer and the p material of the photoelectric conversion layer aresubstantially the same, and a difference in the work function of thefirst buffer layer and the work function of the p material in thephotoelectric conversion layer may be in the range of ±0.2 eV in orderto satisfy both the SN ratio and the afterimage characteristics. In thepresent embodiment, since a quinacridone derivative (BQD) which is a pmaterial having a HOMO level of −5.7 eV is used, the HOMO level of thefirst buffer layer may be in the range of −5.5 eV to −5.9 eV, and theindolocarbazole derivative according to an embodiment of the presentdisclosure may be a useful material satisfying this range.

Example 2 (Preparation of Organic Imaging Element)

An ITO substrate was prepared in the same manner as in Example 1. Afterthe ITO substrate was dried, a UV/ozone treatment was further performedfor 10 minutes. Then, after the ITO substrate was fixed in the substrateholder of the vapor deposition apparatus, the vapor deposition tank wasdepressurized to 5.5×10⁻⁵ Pa. Thereafter, a first buffer layer having afilm thickness of 10 nm was formed by vacuum deposition using a shadowmask using the materials of Compound A, C and E. Then, 2 Ph-BTBT,fluorinated subphthalocyanine chloride (F6-SubPc-Cl), and C60 wereco-deposited to a thickness of 200 nm at a deposition speed ratio of4:4:2 to form a photoelectric conversion layer by a mixed layer (bulkhetero structure) of a p-type organic semiconductor and an n-typeorganic semiconductor. Subsequently, B4PyMPM was deposited to athickness of 10 nm to form a second buffer layer. Thereafter, the secondbuffer layer was placed in a container that can be transported in aninert atmosphere, transported to a sputtering apparatus, and ITO wasdeposited to a thickness of 50 nm on the upper layer of B4PyMPM to forma second electrode. Thereafter, in a nitrogen atmosphere, annealingwhich simulates a process for forming the actual imaging element andapparatus, particularly, a heating process such as installation of acolor filter, installation of a protective film, soldering of an elementand the like was performed at 150° C. for 3.5 hours to prepare anorganic imaging element.

(Evaluation of Organic Imaging Element)

The organic imaging element obtained here was placed on a prober stagecontrolled to a temperature of 95° C., and irradiation of white lightcorresponding to 2000 times normal light was performed while applying avoltage of −2.6 V to the second electrode and the first electrode, andthereby the dark current of the organic imaging element was measured.The dark current value at the start of measurement was defined asJ_(dk0), the dark current value after 12 hours passed was defined asJ_(dkE), and the dark current change during the present test was definedas ΔJ_(dk)=|(J_(dkE)−J_(dk0))/J_(dk0)×100| to perform the evaluation.The results are shown in Table 2. Three materials of Compounds A, C andE were evaluated, and a change in dark current of Compounds C and E wassuppressed as compared with Compound A. This is considered that, ascompared to a carbazole skeleton of Compound A, Compounds C and E havean indolocarbazole skeleton as the mother skeleton, and the size of themother skeleton in the whole molecule is large, and there is nomolecular rotation of the mother skeleton itself due to heat, light andvoltage, and no change in the molecular structure of the motherskeleton, and thus the thin film form of the first buffer layer can bemaintained even when three loads of heat, light and voltage are applied,and also, a change in dark current can be suppressed even when threeloads of heat, light and voltage are applied. It has been found that, inthe conventional technology, resistance to a process of forming theimaging element, particularly, heating processes such as particularlythe installation of the color filter, the installation of the protectivefilm, the soldering of the element and the like, and preservability canbe improved by using a material having a glass transition temperature of140° C. or more for a buffer layer, but when the glass transitiontemperatures of Compounds A and C shown in Table 1 are compared, theglass transition temperatures of Compound A was rather higher, andthereby it turns out that a glass transition temperature is not a majorfactor with respect to resistance to three loads of heat, light, andvoltage.

It can be seen from Examples 1 and 2 that, when an indolocarbazolederivative compound is used in the first buffer layer, not only theinitial characteristics of the SN ratio and afterimage characteristicsare excellent, but also degradation of electric characteristics can besuppressed even in the reliability test in which three loads of “light,voltage and heat” are applied simultaneously and continuously.

Example 3 (Method of Evaluating Absorption Rate of First Buffer LayerContaining Indolocarbazole Derivative)

A spectroscopic measurement was performed to measure light absorption inthe visible light region when the indolocarbazole derivative wasthinned. Specifically, thin films formed of indolocarbazole derivativecompounds (compounds C, D and E) having a thickness of 50 nm was formedon a quartz substrate by a vacuum deposition method, and a lighttransmittance measurement and light reflectance measurement were carriedout to obtain a light absorption spectrum (light absorption rate)calculated in the case in which the film thickness is 10 nm.

(Evaluation Result of Absorption Rate of First Buffer Layer ContainingIndolocarbazole Derivative)

Table 3 and FIG. 4 show the measurement results of the absorption rateof the thin film at the film thickness of 10 nm according to anembodiment of the present disclosure. FIG. 4 shows a change inabsorption rate of the thin film in the wavelength region from 350 nm to700 nm. In the case of the indolocarbazole material according to anembodiment of the present technology, almost no absorption is confirmedin the visible light region of a wavelength longer than 450 nm.Furthermore, the wavelength region from 450 nm to 400 nm is a regioncorresponding to blue light, but as shown in Table 3, in the lightabsorption at 450 nm, 425 nm and 400 nm of Compounds C, D, and E whichare the indolocarbazole derivatives according to an embodiment of thepresent technology, even the highest light absorption is suppressed to1% or less. That is, it can be seen that the thin film of theindolocarbazole derivative according to an embodiment of the presenttechnology has almost no absorption in the visible light region, hasexcellent light absorption characteristics, and a photoelectricconversion function is not inhibited with respect to the imaging elementand photoelectric conversion layer located under the first buffer layeras viewed from the light-incident direction in the imaging element.Physical property values and electrical characteristics of the materialof the first buffer layer used in Example 1 are shown in the followingTable 1. Further, the results of the reliability test of Example 2 areshown in the following Table 2.

TABLE 1 Physical properties Electrical characteristics Glass External

transition Hole Dark current efficiency Afterimage temperature HOMO LUMOmobility (relative (relative SN To (relative (° C.) (eV) (eV) (cm2/Vs)value) value) ratio value) Compound A 189 −5.3 −2.1 2.02E−06 1.00 1.003.76 1.00 Compound B 176 −5.4 −2.1 5.50E−06 0 79 1.01 3.87 Compound C174 −5.5 −2.3 1.00E−05 0.63 1.00 3.96 0.95 Compound D 184 −5.5 −2.33.24E−06 0.42 1.01 4.14 0.96 Compound E 207 −5.6 −2.4 1.50E−05 0.48 0.964.06 1.02 Compound F 203 −6.0 −2.9 0.39 0.91 4.13 2.12

indicates data missing or illegible when filed

TABLE 2

 Jdk Compound A 32.90% Compound C 9.30% Compound E 0.80%

TABLE 3 400 nm 425 nm 450 nm Compound C 1.04% 0.02% 0.01% Compound D0.23% 0.04% 0.01% Compound E 0.08% 0.01% 0.01%

The structure of C60 is provided in FIG. 6.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

REFERENCE SIGNS LIST

-   1 (1-1 to 1-3) imaging element-   20 substrate-   21 anode (first electrode)-   22 first buffer layer-   23 photoelectric conversion layer-   24 second buffer layer-   25 cathode (second electrode)-   31 insulator

Additionally, the present technology may also be configured as:

(A1)

An imaging device, including: an upper electrode; a lower electrode; aphotoelectric conversion layer disposed between the upper electrode andthe lower electrode; and a first organic semiconductor materialincluding an indolocarbazole derivative and disposed between the upperelectrode and the lower electrode.

(A2)

The imaging device according to (A1), where the first organicsemiconductor material is disposed between the photoelectric conversionlayer and the lower electrode.

(A3)

The imaging device according to any of A(1) to A(2), where theindolocarbazole derivative is selected from the group consisting of

where in the formulas (1) to (10), the Ar₁ to Ar₂₄ each independentlyrepresent an aryl group; and R₁ to R₁₀₈ each independently represent ahydrogen group, an alkyl group, an aryl group, an arylamino group, anaryl group having an arylamino group as a substituent, or a carbazolylgroup.

(A4)

The imaging device according to any of A(1) to A(3), where the formulas(1) to (10) are further selected from the group consisting of

(A5)

The imaging device according to any of A(1) to A(4), where the formulas(1) to (10) are further selected from the group consisting of

(A6)

The imaging device according to any of A(1) to A(5), where the formulas(1) to (10) are further selected from the group consisting of

(A7)

The imaging device according to any of A(1) to A(6), where a highestoccupied molecular orbital level or work function of a p-typesemiconductor contained in the photoelectric conversion layer is −5.6 eVto −5.7 eV.

(A8)

The imaging device according to any of A(1) to A(7), where a differencebetween a highest occupied molecular orbital level of the first organicsemiconductor material and a highest occupied molecular orbital level orwork function of a p-type semiconductor contained in the photoelectricconversion layer is in the range of ±0.2 eV.

(A9)

The imaging device according to any of A(1) to A(8), where a differencebetween a highest occupied molecular orbital level of the first organicsemiconductor material and the highest occupied molecular orbital levelor the work function of the p-type semiconductor is in the range of ±0.2eV

(A10)

The imaging device according to any of A(1) to A(9), where anindolocarbazole skeleton of the indolocarbazole derivative hasintramolecular symmetry and a 5-membered pyrrole ring.

(A11)

The imaging device according to any of A(1) to A(10), where a motherskeleton of the indolocarbazole derivative has a large size and has nomolecular rotation when heat, light and voltage are applied to themother skeleton.

(A12)

The imaging device according to any of A(1) to A(11), where the motherskeleton of the indolocarbazole derivative has no molecular rotationwhen heat, light and voltage are applied simultaneously to the motherskeleton.

(A13)

The imaging device according to any of A(1) to A(12), where the firstorganic semiconductor material is an electron blocking layer.

(A14)

The imaging device according to any of A(1) to A(13), where the upperelectrode includes indium-zinc oxide.

(A15)

The imaging device according to any of A(1) to A(14), where the lowerelectrode includes indium-tin oxide.

(A16)

The imaging device according to any of A(1) to A(15), where thephotoelectric conversion layer includes at least two materials selectedfrom the group consisting of a naphthalene derivative, an anthracenederivative, a phenanthrene derivative, a pyrene derivative, a perylenederivative, a tetracene derivative, a pentacene derivative, aquinacridone derivative, a picene derivative, a chrysene derivative, afluoranthene derivative, a phthalocyanine derivative, asubphthalocyanine derivative, a metal complex having a heterocycliccompound as a ligand, a thienoacene material typified by abenzothienothiophene (BTBT) derivative, a dinaphthothienothiophene(DNTT) derivative, a dianthracenothienothiophene (DATT) derivative, abenzobisbenzothiophene (BBBT) derivative, a thienobisbenzothiophene(TBBT) derivative, a dibenzothienobisbenzothiophene (DBTBT) derivative,a dithienobenzodithiophene (DTBDT) derivative, adibenzothienodithiophene (DBTDT) derivative, a benzodithiophene (BDT)derivative, a naphthodithiophene (NDT) derivative, ananthracenodithiophene (ADT) derivative, a tetracenodithiophene (TDT)derivative, a pentacenodithiophene (PDT) derivative, and a compoundrepresented by the following formula (11)

where, R₁₀₉ to R₁₁₂ each independently represent a hydrogen group, analkyl group, an aryl group, an arylamino group, or a carbazolyl group,organic semiconductors having HOMO levels and LUMO levels higher thanthose of p-type organic semiconductors, transparent inorganic metaloxides, a heterocyclic compound containing a nitrogen atom and an oxygenatom and a sulfur atom, organic molecules, organometallic complexes andsubphthalocyanine derivatives having pyridine, pyrazine, pyrimidine,triazine, quinoline, quinoxaline, isoquinoline, acridine, phenazine,phenanthroline, tetrazole, pyrazole, imidazole, thiazole, oxazole,benzimidazole, benzotriazole, benzoxazole, carbazole, benzofuran,dibenzofuran, fullerenes, and fullerene derivatives.

(A17)

The imaging device according to any of A(1) to A(16), further including:a second organic semiconductor material disposed between thephotoelectric conversion layer and the upper electrode, where the secondorganic semiconductor material includes at least one of pyridine,quinoline, acridine, indole, imidazole, benzimidazole, phenanthroline,and fullerenes and derivatives thereof having absorption in the visiblelight region from 400 nm to 700 nm and typified by C60 and C70.

(A18)

The imaging device according to any of A(1) to A(17), wherein theindolocarbazole derivative includes at least two indole rings in onemolecule.

(A19)

The imaging device according to A(1), further comprising: a firstsemiconductor material is disposed adjacent to the first organicsemiconductor material.

(A20)

The imaging device according to A(19), wherein the first semiconductormaterial comprises at least one material selected from the groupconsisting of triarylamine compounds, benzidine compounds, styrylaminecompounds, carbazole derivatives, naphthalene derivatives, anthracenederivatives, phenanthrene derivatives, pyrene derivatives, perylenederivatives, tetracene derivatives, pentacene derivatives, picenederivatives, chrysene derivatives, fluoranthene derivatives,phthalocyanine derivatives, subphthalocyanine derivatives,hexaazatriphenylene derivatives, metal complexes having a heterocycliccompound as a ligand, thienoacene materials typified bybenzothienothiophene (BTBT) derivatives, dinaphthothienothiophene (DNTT)derivatives, dianthracenothienothiophene (DATT) derivatives,benzobisbenzothiophene (BBBT) derivatives, thienobisbenzothiophene(TBBT) derivatives, dibenzothienobisbenzothiophene (DBTBT) derivatives,dithienobenzodithiophene (DTBDT) derivatives, dibenzothienodithiophene(DBTDT) derivatives, benzodithiophene (BDT) derivatives,naphthodithiophene (NDT) derivatives, anthracenodithiophene (ADT)derivatives, tetracenodithiophene (TDT) derivatives andpentacenodithiophene (PDT) derivatives,poly(3,4-ethylenedioxythiophene)/polystyrenesulfonic acid (PEDOT/PSS),polyaniline, molybdenum oxide (MoOx), ruthenium oxide (RuOx), vanadiumoxide (VOx), tungsten oxide (WOx).

(A21)

The imaging device according to any of A(1) to A(18), further including:a second organic semiconductor material disposed between thephotoelectric conversion layer and the upper electrode, where the upperelectrode includes indium-zinc oxide, where the lower electrode includesindium-tin oxide, where the photoelectric conversion layer includes 2Ph-benzothienothiophene, subphthalocyanine, and C60, and where thesecond organic semiconductor material includes at least one of pyridine,quinoline, acridine, indole, imidazole, benzimidazole, phenanthroline,and fullerenes and derivatives thereof having absorption in the visiblelight region from 400 nm to 700 nm and typified by C60 and C70.

(A22)

An electronic apparatus, including: a lens; signal processing circuitry;and an imaging device, including: an upper electrode; a lower electrode;a photoelectric conversion layer disposed between the upper electrodeand the lower electrode; a first organic semiconductor materialincluding an indolocarbazole derivative and disposed between the upperelectrode and the lower electrode.

1-23. (canceled)
 24. A light detecting device, comprising: a firstelectrode; a second electrode; a photoelectric conversion layer disposedbetween the first electrode and the second electrode; and a first bufferlayer comprising an indolocarbazole derivative, the first buffer layerbeing disposed between the first electrode and the photoelectricconversion layer.
 25. The light detecting device according to claim 24,wherein the photoelectric conversion layer comprises a first organicsemiconductor having a highest occupied molecular orbital level or awork function, the highest occupied molecular orbital level of the firstorganic semiconductor being shallowest highest occupied molecularorbital level in the photoelectric conversion layer or the work functionof the first organic semiconductor being shallowest working function inthe photoelectric conversion layer.
 26. The light detecting deviceaccording to claim 25, wherein the highest occupied molecular orbitallevel or the work function of the first organic semiconductor is −5.6 eVto −5.7 eV.
 27. The light detecting device according to claim 25,wherein a difference between a highest occupied molecular orbital levelor a work function of the indolocarbazole derivative and the highestoccupied molecular orbital level or the work function of the firstorganic semiconductor is in the range of ±0.2 eV.
 28. The lightdetecting device according to claim 25, wherein the first organicsemiconductor is a p-type semiconductor.
 29. The light detecting deviceaccording to claim 24, wherein the indolocarbazole derivative isselected from the group consisting of:

wherein in the formulas (1) to (10), Ar1 to Ar24 each independentlyrepresent an aryl group; and R1 to R108 each independently represent ahydrogen group, an alkyl group, an aryl group, an arylamino group, anaryl group having an arylamino group as a substituent, or a carbazolylgroup.
 30. The imaging device according to claim 29, wherein theformulas (1) to (10) are further selected from the group consisting of:


31. The imaging device according to claim 29, wherein the formulas (1)to (10) are further selected from the group consisting of:


32. The imaging device according to claim 29, wherein the formulas (1)to (10) are further selected from the group consisting of:


33. The imaging device according to claim 24, wherein an indolocarbazoleskeleton of the indolocarbazole derivative has intramolecular symmetryand a 5-membered pyrrole ring.
 34. The imaging device according to claim24, wherein a mother skeleton of the indolocarbazole derivative has alarge size and has no molecular rotation when heat, light and voltageare applied to the mother skeleton.
 35. The imaging device according toclaim 34, wherein the mother skeleton of the indolocarbazole derivativehas no molecular rotation when heat, light and voltage are appliedsimultaneously to the mother skeleton.
 36. The imaging device accordingto claim 24, wherein the second electrode comprises indium-zinc oxide.37. The imaging device according to claim 24, wherein the firstelectrode comprises indium-tin oxide.
 38. The imaging device accordingto claim 24, further comprising a first semiconductor material disposedadjacent to the first organic semiconductor material.
 39. The imagingdevice according to claim 38, wherein the first semiconductor materialcomprises at least one material selected from the group consisting oftriarylamine compounds, benzidine compounds, styrylamine compounds,carbazole derivatives, naphthalene derivatives, anthracene derivatives,phenanthrene derivatives, pyrene derivatives, perylene derivatives,tetracene derivatives, pentacene derivatives, picene derivatives,chrysene derivatives, fluoranthene derivatives, phthalocyaninederivatives, subphthalocyanine derivatives, hexaazatriphenylenederivatives, metal complexes having a heterocyclic compound as a ligandthienoacene materials typified bybenzothienothiophene (BTBT)derivatives, dinaphthothienothiophene (DNTT) derivatives,dianthracenothienothiophene (DATT) derivatives, benzobisbenzothiophene(BBBT) derivatives, thienobisbenzothiophene (TBBT) derivatives,dibenzothienobisbenzothiophene (DBTBT) derivatives,dithienobenzodithiophene (DTBDT) derivatives, dibenzothienodithiophene(DBTDT) derivatives, benzodithiophene (BDT) derivatives,naphthodithiophene (NDT) derivatives, anthracenodithiophene (ADT)derivatives, tetracenodithiophene (TDT) derivatives andpentacenodithiophene (PDT) derivatives,poly(3,4-ethylenedioxythiophene)/polystyrenesulfonicacid (PEDOT/PSS),polyaniline, molybdenum oxide (MoOx), ruthenium oxide (RuOx), vanadiumoxide (VOx), and tungsten oxide (WOx).
 40. The imaging device accordingto claim 24, wherein the photoelectric conversion layer comprises atleast two materials selected from the group consisting of a naphthalenederivative, an anthracene derivative, a phenanthrene derivative, apyrene derivative, a perylene derivative, a tetracene derivative, apentacene derivative, a quinacridone derivative, a picene derivative, achrysene derivative, a fluoranthene derivative, a phthalocyaninederivative, a subphthalocyanine derivative, a metal complex having aheterocyclic compound as a ligand, a thienoacene material typified by abenzothienothiophene (BTBT) derivative, a dinaphthothienothiophene(DNTT) derivative, a dianthracenothienothiophene (DATT) derivative, abenzobisbenzothiophene (BBBT) derivative, a thienobisbenzothiophene(TBBT) derivative, a dibenzothienobisbenzothiophene (DB TBT) derivative,a dithienobenzodithiophene (DTBDT) derivative, adibenzothienodithiophene (DBTDT) derivative, a benzodithiophene (BDT)derivative, a naphthodithiophene (NDT) derivative, ananthracenodithiophene (ADT) derivative, a tetracenodithiophene (TDT)derivative, a pentacenodithiophene (PDT) derivative, and a compoundrepresented by the following formula (11)

wherein, R₁₀₉ to R₁₁₂ each independently represent a hydrogen group, analkyl group, an aryl group, an arylamino group, or a carbazolyl group,organic semiconductors having HOMO levels and LUMO levels higher thanthose of p-type organic semiconductors, transparent inorganic metaloxides, a heterocyclic compound containing a nitrogen atom and an oxygenatom and a sulfur atom, organic molecules, organometallic complexes andsubphthalocyanine derivatives having pyridine, pyrazine, pyrimidine,triazine, quinoline, quinoxaline, isoquinoline, acridine, phenazine,phenanthroline, tetrazole, pyrazole, imidazole, thiazole, oxazole,benzimidazole, benzotriazole, benzoxazole, carbazole, benzofuran,dibenzofuran, fullerenes, and fullerene derivatives.
 41. The imagingdevice according to claim 24, wherein the photoelectric conversion layercomprises at least one materials selected from the group consisting ofcrystalline silicon, amorphous silicon, microcrystalline silicon,crystalline selenium, amorphous selenium, and compound semiconductorssuch as chalcopyrite compounds such as CIGS (CuInGaSe), CIS (CuInSe₂),CuInS₂, CuAlS₂, CuAlSe₂, CuGaS₂, CuGaSe₂, AgAIS₂, AgAlSe₂, AginS₂ andAglnSe₂, or group III-V compounds such as GaAs, InP, Al GaAs, InGaP,AlGalnP and InGaAsP, and CdSe, CdS, lmSe₃, In₂S₃, BhSe₃, BhS₃, ZnSe,ZnS, PbSe, PbS, and quantum dots formed of these materials.
 42. Theimaging device according to claim 24, further comprising a second bufferlayer disposed between the photoelectric conversion layer and the secondelectrode, wherein the second buffer layer comprises a compound selectedfrom the group consisting of pyridine, quinoline, acridine, indole,imidazole, benzimidazole, phenanthroline, and fullerenes, andderivatives thereof, and combinations thereof.
 43. An electronicapparatus, comprising: a lens; signal processing circuitry; and a lightdetecting device comprising: a first electrode; a second electrode; aphotoelectric conversion layer disposed between the first electrode andthe second electrode; and a first buffer layer comprising anindolocarbazole derivative, the first buffer layer being disposedbetween the first electrode and the photoelectric conversion layer.